Wave distribution



H. C. EGERTON.'

WAVE DISTRIBUTION.

APPLICATION FILED JULY 26.!91-7.

1,365,470. I Patented Jan. 11,1921.

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WAVE DISTRIBUTION.

APPLICATION FILED IULY 26,19I7.

1,365,470. Patented Jan. 11, 1921.

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STATES PATENT OFFICE.

HENRY C. EGERTON, OF PASSAIC, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

WAVE DISTRIBUTION.

Application filed July 26, 1917.

To all whom it ma concern:

Be it known that l, HENRY C. EGERTON, a citizen of the United States, residin at Passaic, in the county of Passaic and tate of New Jersey, have invented certain-new and useful Improvements in Wave Distribution, of which the following is a full, clear, concise, and exact description.

This invention relates to wave distribution and more particularly to a method and apparatus for transmitting identical messages through a plurality of media having different rates of wave propagation so as to effects at a distant staconditions somewhat where the speakers' voice was completely inaudible it, in some cases, results in interference between the soundwaves produced by the s eakers voice and the sound waves produce by the auxiliary receivers within the limits in which the speakers voice had been but faintly audible previously.

The principalobject of thepresent inven- 1 tion is to provide amethod and apparatus whereby waves may be transmitted to a certain position by two or more different media having unequal rates of wave transmission, so that the same or substantially identical waves will arrive at suchposition in substantial 'synchronism, and this end is accomplished by propagating certain waves in the medium having the lower rate of wave transmission and timing the transmission of the same or substantially identical waves over the medium of higher rate so that the' waves reaching such position by both of such different media arrive thereatinsubstantial synchroni'sm.

, A further object of the invention is to provide a suitable method and apparatus where- Speeification of Letters Patent.

Patented Ja 'n. '11. 1921.

Serial No. 182,964.

by sound waves are produced in one medium at one of a plurallty of sound producing sources, and similar sound waves transmitted by another medium having a different rate of sound wave transmission to other of said sources to reproduce similar sound waves in the first-mentioned medium in synchronism or consonance with the arrival of similar sound waves in this-medium from the firstmentioned source to intensify such sound waves and overcome, to a great extent, the interference heretofore experienced.

To accomplish this object, the method contemplates the provision of two or more sources of sound waves located at different positions to operate in the same medium, and the use of suitable apparatus cooperating with the first of said sources to reproduce substantially identical sound Waves to those produced at the first source and in-the same medium therewith at the second and succeeding sources in synchronism with the arrival of substantially identical sound waves from the preceding sources through the medium in which the sounds are reproduced at the second and succeeding sources.

The method which constitutes the invention is capable of being carried out with a great variety ofapparatus and is not limited( 'to reinforcing, the voice of a speaker, since suitable for sound transmission in large auditoriums; while. Fig. 2 illustrates an arrangement suitable for transmission and synchronization of a message transmitted to a distant station by both wire and wireless.

telephone circuits. Referring to Fig. 1 showing one arrange [ment of apparatus suitable for use in large auditoriums to enable the words of a speaker tov be readily heard at any point therein a speakers platform 10 is shown and the normal position of the speaker indicated by a dotted circle 11. Any suitable sound record- ,I

ing device is arranged in a position to be actuated by the sound vibrations of the speakers voice in air to record the same on any suitable record. The drawing shows a telephonic transmitter 12 operating inductively through an audion amplifier 13 and electromagnetic recorder 14 to record the speakers words upon a telegraphone record disk 14; the record being rotated at a definite rate of speed by any desired means (not shown). The induction coils, associated with the amplifier, serve to step up the voltage with little distortion, while the audion amplifier serves to amplify the current with no distortion whatsoever; while the retardation coils shown are placed in the circuit to prevent the passage of alternating current between the two sides of the line and yet permit the supply of direct current from the battery to the'line. The operation of these devices is well known, however, and no further description thereof is believed necessary to the understanding of the present invention.

Assume that thespeakers voice can be easily and clearly understood over the area A, shown on the drawing, whereas the speakers voice is faint within the area B; unintelligible for the most part throughout the area C, and inaudible beyond the area C.

It is well known that sound waves have the definite velocity of 1,090 feet per second in still air at 32 Fahrenheit, which results in an appreciable difference in the time it takes the speakers voice to reach different parts of a large auditorium or the like. This time interval should be compensated for in intensifying or producing substantially identical sound waves at two or more places in the same auditorium. The present method accomplishes this by producing sound waves in air at one position and reproducing identical sound waves in air at the second and succeeding positions at the instant the particular sound waves from the first position reach the second and succeeding positions through the air medium. The succeeding positions are preferably arranged so that the successive reproduction in air thereat will also coincide with the arrival of the identical sound waves through the air from all the preceding positions at the position being considered.

Therefore, to enable those within the area B to hearthe speakers words easily it is necessary tolocate a sound reproducer at the forward limit of B and arran e it to reproduce the identical words of t e speaker at the moment the original sound waves from the speaker reach the reproducer, whereby the words reproduced reinforce and intensify the actual words of the speaker and render them loud enough to be easily heard throughout the area B. To accomplish this with the apparatus illustrated, an electromagnetic reproducer 16 is adj ustably mounted with respect to the record 15 and inductively associated with an audion amplifier 17 which operates a loud speaking receiver 18. The reproducer 16 would be adjusted to reproduce the recorded sound waves at the receiver 18 at the same instant as the original sound waves from the speaker reach the receiver and as the rate of electrical transmission is much more rapid over the circuit between the reproducer 16 and the receiver 18, than the travel of sound waves in air, the reproducer 16 is positioned to delay the reproduction at the receiver 18 sufficiently to compensate for the difierent rates of wave transmission over the two dif ferent media. If desired, a number of loud speaking receivers can be arranged in parallel with the receiver 18 and located at the same distance from the speaker. The horns of the receivers 18 would preferably be directed in the same direction as' the sound waves from the speakers voice to minimize interference between sound waves in air from the different sources traveling in an opposite direction to those from the primary source. This principle should also be applied, as far as possible, in positioning the secondary sound producers.

The sound reaching the areav 0 would be similarly intensified and rendered intelligible through a similar adjustable reproducer 16 operating through an amplifier 17 and receiver 18 adjusted so as to reproduce certain sound waves in air at the same instant that/ substantially identical sound waves traveling in air reach the receiver 18 from the speaker and the next preceding receiver 18. A similar arrangement of electromagnetic reproducer 16 am- 105 plifier l7 and receiver 18 operates in asimilanmanner to render the words of the speaker clearly audible to those in the rear of the'area C. Individual hand or head receivers may be used in place of the loud 110 speaking receive-rs, or both loud speaking and individual receivers used together, if desired. 4

An electromagnetic eraser 19 may be operated to obliterate the magnetic record on 115 the disk 15 as soon as it has been reproduced, or the eraser may be omitted and a wire or wire-disk record used which admits of keeping the record for further reproductionin the same way as ordinary phonographic torium there would be no speaker, but it would be desirable to reproduce the same at a number of different places in the auditorium to render it audible throughout. In this case the receiver 18 would be the first to reproduce the record in the air while the reproducers 16' and 16 would be adjusted so as to reproduce the same part of the record in air at the same instant such particular sound waves from the receiver 18 traveling through the air would reach the receivers 18 and 18 respectively.

In some cases it may also be found desirable to augment the speakers voice at substantially the same position at which he is speaking, either in connection with or independently of reproduction of his words in other parts of an auditorium or the like, as previously described. To accomplish this result with the apparatus shown, it is only necessary to connect a loud speaking receiver 20 to receive fluctuating current proportional to the fluctuations produced by the speakers voice in the transmitter 12. This may be done in a variety of ways as, for example, by connecting the receiver across the secondary of the induction coil connected to the recorder 1 and in parallel therewith, as shown. Owing to the high speed of electrical transformation and amplification, as compared with the velocity of sound in air, the sound waves produced in the air by the receiver 20 would coincide with those of thespeaker'to such an extent as to render any theoretical interference of sound waves impossible of detection. To prevent singing occurring by locating the transmitter 12 and the receiver 20 in close proximity it is preferable that the transmitter 12, in such'a case, be a chest or throat transmitter which will be unaffected by the 7 sound produced by the adjacent receiver 20.

It is not necessary in the carrying out of the method by a telegraphone that the curlg'rent be amplified either before or after being recorded on the recorder 15, but more satisfactory results are obtained thereby.

In telephonically transmitting a message I from one station to another over a loaded" wire telephone circuit the rate oftransmission through the medium of the wire circuit is low as compared to the rate of transmission of messages by wireless telephone waves through'the medium of the ether; the rate in the latter case being about threetimes that in the former. Under this situation, if

a message is to be sent from one station to another both by wire and wireless telephstation in synchronism with the substantially identical sound waves transmitted thereto over the wire circuit.

One simple arrangement suitable for this purpose is shown in Fig. 2. In this construction a microphone 30, serves to vary the current flow through the primary winding of an induction coil 31; the secondary winding of which is connected to an electromagnetic recorder 32. A record corresponding to the variations received by the re corder 32 is transferred thereby to a teleg-- raphone record or disk 33, driven at a definite rate of speed by any suitable means (not shown). An electromagnetic reproducer 34 is arranged in operative relation to the record 33 and inductively associated through an induction coil '35 with an audion amplifier 36. This amplifier is in turn inductively connected through another induction coil 37 with a line circuit 38, with which the telephone receiver 39 at the distant receiving station is operatively associated in any suitable manner. Inasmuch as the receiver 39 would be located at a considerable distance from the sending station, under the conditions assumed, a considerable amount of apparatus would intervene in the wire circuit between the sending and receiving station but as such apparatus is well known and forms no part of the present invention no detailed showing thereof is considered necessary..

Since the rate of wave transmission through the medium of the ether is about three times that through the medium of a wire circuit, it is necessaryv to compensate for this difference if sound waves transmitted by both Wire and wireless circuits are to be reproduced in synchronism at the receiving station. This may be accomplished either by delivering the high frequency waves to the ether a definite period after the delivery of similar waves to the wire circuit or by delivering the waves to both the wire and radio circuits at thesending station, then, recording the waves transmittedby the ether at the receiving station and reproducing the recorded waves thereat .a definite period thereafter so as to synchronize with. the arrival thereof of similar wavestransmitted by the wire circuit.

In the particular s stem illustrated, the radio transmission 0 the high frequency waves is delayed by positioning a second electromagnetic reproducer .40 so as to re produce the same portion of the record 33 at such an interval after. the reproducer 34 as to compensate for the difference in rate between wire and radio transmission. To facilitate obtaining the proper relationship between the reproducers 34 and L0, the two are preferably arranged so that they can be adjusted relatively to each other to vary the interval between them according to the dilfe ence in time of transmission by wire and radio circuits between the sending station and any one of a number of different receiving stations with which communication might be had.

Any suitable wireless sending and receiving apparatus may be employed for radio transmission, but the particular apparatus ducer 46 and its secondary winding included in the input circuit of the modulator 42,

serves to impress the oscillations developed in the reproducer 40 by the record 33 upon this input circuit. Under the influence of these different oscillations the modulator 42 develops modulated high frequency oscilla- 'tions in its output circuit which, through the medium of an induction coil 45, are impressed upon the input circuit of a group of vacuum tube amplifiers 46, arranged in parallel. These amplifiers produce augmented high frequency oscillations in their output circuit and an induction coil 47 transfers such oscillations to the sending antenna 48, through which electromagnetic waves are originated in the ether for trans mission to the receiving station.

These waves impinge upon the antenna 49 of the receiving station and are transferred by means of an induction coil 50 to the input circuit of an amplifier 51 by which the energy of oscillations in the output circuit is increased over that received in the input circuit. An induction coil 52 acts to transfer this increased energy to the input circuit of a thermionic element 53 which operates to detect the incoming high frequency modulated oscillations and to transmit only low frequency oscillations corresponding to the waves developed by the telegraphone record 33 to the output circuit. This output circuit includes the primary winding of an induction coil 54, and a loud speaking telephone receiver 55 in circuit with the secondary Winding of this coil, serves to reproduce these low frequency oscillations as articulate sound waves.

The receivers 39 and 55 at the receiving station are preferably arranged adjacent to each other, and from the foregoing description it will be apparent that identical messages transmitted to' the receiving station by wire and radio circuits can be reproduced in consonance thereat; the message reproduced by the receiver 39 reinforcing that reproduced by the receiver 55 and vice versa. If desired to erase the matter recorded on the record 33 after reproduction thereof, an electromagnetic eraser 56 may be provided for this purpose.

What is claimed is:

1. The method of transmitting intelligence from one station to another station by a plurality of media having different rates of wave propagation which consists in producing impulses in one medium at one station for transmission thereby to said other station, in utilizing such impulses to produce impulses-corresponding thereto, in recording said corresponding impulses upon a rec- 0rd capable of immediate reproduction, in subsequently reproducing said recorded impulses at said other station coincident with the arrival thereat of and in consonance with the original impulses transmitted by said first medium, and in utilizing a second medium having a higher rate of wave propagation than the first medium in the transmission of impulses between said record and one of said stations.

2. The method of transmitting intelligence from one station to another station by a plurality of media having diiferentrates of wave propagation which consists in producing impulses at one station in one of said media for transmission thereby to said other station, inxutilizing said impulses to produce impulses corresponding thereto, in recording said corresponding impulses upon a record capable of immediate reproduction, in timing the reproduction of said recorded impulses in another medium having a relatively high rate of wave propagation to compensate for the difference in rates of propagation between said two media, and in translating said reproduced impulses into corresponding impulses in said first mentioned medium at said other station to coincide with the arrival thereat of the original impulses transmitted over saidfirst mentioned medium.

3. The method of transmitting intelligence from one station to anotherstation by two media having different rates of wave propagation which consists in producing impulses at one station in the medium having the lower rate of propagation for transmission thereby to said other station, recording said impulses upon a record capable of immediate reproduction, and delaying the reproduction of said recorded impulses in the medium having the higher rate of propagation so that the arrival of said reproduced impulses at said distant station will coincide with the arrival thereat of the original impulses transmitted over the medium having the lower rate of propagation.

4. The method of sound distribution which consists in producing sound Waves at one position in one medium for transmission thereby to another position, reproducing said sound waves at substantially the position of original production and in substantial consonance with the original sound waves,'recording said sound waves upon a record capable of immediate reproduction, separately transmitting corresponding waves to said other position by another medium having a higher rate of wave production than said first medium, in timing the reproduction of said recorded waves in said second medium to compensate for the difference in rates of wave production between said medium, and in translating said reproduced wavesinto corresponding sound waves in said first mentioned medium at said other position to coincide with the arrival thereat of the original sound waves transmitted over said first mentioned medium.

5. The method of sound distribution which consists in producing sound waves at one position in air for transmission thereby to another position, reproducing said sound waves at substantially the position of original production and in substantial consonance with said sound waves recording said sound waves upon a record capable of immediate reproduction, separately transmitting waves corresponding to said recorded sound waves to said other position by another medium having a higher rate of wave propagation than air, in timing the reproduction ofsaid recorded waves in said second medium to compensate for the difference in rates of wave propagation between air and said medium, and in translating said reproduced waves into corresponding sound waves .in air at said other position to coincide with the arrival thereat of the original sound waves transmitted thereto by air. a

6. A system of sound distribution ,comprising a transmitting station, means thereat to impress waves upon one medium for transmission thereby to another station, means to impress corresponding waves upon another medium having a different rate of, wave propagation than said first medium, means responsive to waves transmitted thereto by one of said media to record such waves and including a record capable of immediate reproduction, means toreproduce corresponding waves from said record, and means to time the arrival at said other station of said reproduced waves to synchronize with the arrival thereat of consonant waves trans- 7 mitted thereto by the other sa1d media.

.7. The method of sound distribution which consists in producing sound waves in air, recordingsaid sound waves, separately transmitting waves derived from and corresponding to said recorded sound waves to a distant point by another medium having a 7 higher rate of wave transmission 'thanair,

and timing the arrival of said separately prising a main transmitting station, means for recording sounds emitted at said station including a record capable of use to reproduce matter recorded thereon immediately subsequent to recording thereof, reproducing means responsive to said sound record and adapted to reproduce said record at a definite period of timeafter the recording thereof, and sound producing. means at another station responsive to said reproducing means to reproduce said recorded sounds colncident with the arrival thereat of and in consonance with thesounds emitted by said main station; whereby said emitted sounds and those developed by said sound producing means reinforce each other without interference at such other station.

9. A system of sound distribution comprising a main transmitting station, a plurality of outlying reproducing stations, an intermediate means for recording sounds emitted at said main station and for transmitting waves corresponding thereto to said outlying stations in a definite order'depending upon the respective distances of. said outlying stations from said main transmitting station, said intermediate means including a recorded thereon immediately subsequent to recording thereof, andmeans at each of said outlying stations responsive to said transmitted waves to reproduce said recorded sounds at its respective station coincident with the arrival of and in consonance with. the sounds emitted at said mam station,

record of sounds emitted at said transmitting station and including an amplifier to amplify the current changes produced by said microphonic element, an outlying reproduc- .record capable of use to reproduce matter ing statipn, and means cooperating with said 'sound record to reproduce said recorded sounds at said outlying station a predetermined time after the original production thereof at said main transmitting station and coincident with the. arrival at said outlying station of and in consonance with the original. sounds emitted at said main statfon.

In witness whereof, I hereunto subscribe myname this 24th day of July A. D., 1917. HENRY c. EGERTON, 

